It is widely recognized that digital communications technology and data processing technology are converging. One example of this is the development of portable personal computers that include telephone modems, enabling the transmission of digital information over public switched telephone networks (PSTN). Another example is the development of mobile radio telephones that use microprocessors executing stored programs for sampling and digitizing the voice signal, multiplexing the transmission of the digitized voice signal with other such voice signals, and digitally controlling the operations of the cellular telephone device.
The most recent evidence of the convergence of digital communications technology with digital personal computer technology, is the SIMON personal communications device described in the above identified patent applications. The SIMON personal communications device has many features within it to enable personal communications. The personal communications device provides a cellular telephone, a facsimile transmission and receiving capability, an electronic mail sending and receiving capability, and an electronic pager, a computer notepad, a computer address book, a computer calendar, and a computer calculator, all within a single compact portable package.
The SIMON personal communications device includes a central processing unit (CPU) that executes stored programmed instructions stored in electrically programmable read only memories (EPROM). The stored program instruction in the EPROM's include basic input output operating system (BIOS) programs, and application programs to perform the functions of cellular telephony, public switched telephone network (PSTN) telephony, facsimile transmission and reception, electronic mail, pager functions, computer notepad functions, computer address book functions, computer calendar functions, and computer calculator functions. These stored programs are selectively accessed for execution by the CPU.
The SIMON personal communications device also includes a liquid crystal display having a touch overlay membrane, to enable the user to input keyboard entries or sketches by tactile pressure with a finger or proximity with a stylus. One example of a touch overlay membrane input device is described in U.S. Pat. No. 4,686,332 by Evon Greanias, et al., entitled "Combined Finger Touch and Stylus Detection System for Use on the Viewing Surface of a Visual Display Device", assigned to the IBM Corporation and incorporated herein by reference.
The storage capacity of the RAM can be augmented by employing supplementary memory in the form of a personal computer memory card (PCMCIA) (Trademark of the Personal Computer Memory Card International Association). The personal computer memory card can include extra RAM to supplement the RAM storage in the personal communications device, by plugging the personal computer memory card into a PCMCIA receptacle slot in the personal communications device.
The LCD screen presents menu images to the user to enable the selection of communications applications such as telephone, facsimile (FAX), or electronic mail (E-mail). For each of these applications, a corresponding keypad and presentation area is displayed. The user has the option of employing either a public switched telephone network link or a cellular telephone network link for any of these communications applications. However, the functions required to be performed in order to send or receive a cellular telephone network call are different from the functions required for a call over a public switched telephone network.
All cellular telephones use two-way radio communications controlled by the cellular telephone network. The ambient atmospheric and geographic conditions can affect the strength of the transmitted signal. When transmitting a large amount of data during a FAX or an E-mail session, an acceptable signal strength is required to ensure that data is not lost and to keep the transmission error-free. A signal strength indicator is required on cellular telephones to enable the user to monitor the signal strength and change its location to improve it. Further, a cellular telephone must be registered with the home region it usually employs as the base for its communications. If the cellular telephone is transported outside of its home region, it becomes a roamer, and a different mode of operation called roaming, is carried out. A cellular telephone must provide an indication to the user as to its current mode of operation, either home or roaming. Such concerns are absent from calls using a public switched telephone network.
The personal communications device requires the ability to selectively reconfigure itself, based on the input and output connections attached to it by the user and based on the communications applications selected by the user.